I ran across this issue today when testing some Swift code against an old iPad 2 (I think it's an iPad 2 -- it's model MD368LL/A), running iOS 8.1.3. It turned out that the problem existed everywhere that I was calling something like:

Int(arc4random() % <someInt>)

This worked fine on later iPads, iPhone5S, iPhone6, etc. Fixed by changing code to: